ABSTRACT
Accelerated acute cellular rejection (AR) continues to be a serious problem in kidney transplantation (KT), suggesting that undetected presensitization may be encountered. The purpose of this study was to determine the most sensitive crossmatching (XM) technique to detect the preformed antibody (Ab) which may cause AR. One hundred and twenty two sera from 98 patients, on the waiting list for KT at Ramathibodi Hospital were XMed with 23 cadaveric splenic lymphocytes including 2 living related KT (LR-KT). The XM was performed by 3 different techniques namely, standard microlymphocytotoxicity test (standard NIH), antihuman globulin microlymphocytotoxicity test (AHG) and flow cytometric XM (FCXM). The XM results revealed that 8 out of 75 (10.7%) tests were negative by standard NIH, i.e., 5 tests were positive by AHG only and 1 test was positive by FCXM only and 2 tests were positive by both AHG and FCXM. In addition, the patients who had the AHG technique were not done, 5 out of 47 (10.7%) tests were also negative by standard NIH but were positive by FCXM. The sensitivity of the techniques was done by titrations of anti HLA-A2. It was found that FCXM was the most sensitive technique, followed by AHG and standard NIH, consecutively. In the retrospective study of LR-KT, case #1, the standard NIH for XM using pre-KT blood sample was negative while AHG and FCXM were strongly positive. The patient had AR at day 2 post-KT which confirmed by needle biopsy. The serum at day 11 and day 116 post-KT were tested again and were positive by the 3 techniques. Case #2, pre-KT blood sample showed negative T-XM by the 3 techniques while auto-B and B-XM were positive by standard NIH and AHG but negative by FCXM. This patient had rejection at day 16 after KT. The post-KT blood sample at day 30 showed positive auto T/B and T/B-XM by standard NIH and AHG whereas it was still negative by FCXM. It was also noted that Ab to donor B cell was better detected by standard NIH and AHG than FCXM. In conclusion, FCXM is more sensitive than standard NIH and AHG, however this technique is limited in detecting IgM T and B cell Ab. AHG technique can detect both IgG and IgM antidonor T and B cell Abs. In addition, AHG technique is more sensitive than standard NIH and does not require sophisticated equipment. AHG technique should be appropriate for routine XM, especially, in LR-KT and sensitized patients.